Continuous noninvasive arterial pressure measurement using the volume clamp method: an evaluation of the CNAP device in intensive care unit patients

The CNAP system allows continuous noninvasive arterial pressure measurement based on the volume clamp method using a finger cuff. We aimed to evaluate the agreement between arterial pressure measurements noninvasively obtained using the CNAP device and arterial catheter-derived arterial pressure measurements in intensive care unit patients. In 55 intensive care unit patients, we simultaneously recorded arterial pressure values obtained by an arterial catheter placed in the abdominal aorta through the femoral artery (criterion standard) and arterial pressure values determined noninvasively using CNAP. We performed Bland–Altman analysis and calculated the percentage error. The mean difference (±standard deviation, 95 % limits of agreement, percentage error) between noninvasive (CNAP) and invasively assessed arterial pressure was for mean arterial pressure +1 mmHg (±9 mmHg, −16 to +19 mmHg, 22 %), for systolic arterial pressure −10 mmHg (±16 mmHg, −42 to +21 mmHg, 27 %), and for diastolic arterial pressure +7 mmHg (±9 mmHg, −10 to +24 mmHg, 28 %). Our results indicate a reasonable accuracy and precision for the determination of mean and diastolic arterial pressure by noninvasive continuous arterial pressure measurements using the volume clamp method compared with the criterion standard (invasive arterial catheter). Systolic arterial pressure is determined less accurately and precisely.